The subject matter disclosed herein generally relates to gas turbine engines and, more particularly, to tangential on-board injectors (TOBI).
Variable Area Turbines (VATs) are an adaptive component which, when coupled with other adaptive engine features such as adaptive fans, compressors with variable vanes, variable nozzles, etc. can yield significant benefits in overall gas turbine engine performance. Such benefits may include but are not limited to reduced specific fuel consumption (SFC), reduced High Pressure Compressor (HPC) discharge air temperature (T3) at take-off conditions, improved throttle response, and improved part life. A VATs function is to provide a change in turbine flow parameter (i.e., HPT flow parameter is defined as FP4, LPT flow parameter is defined as FP45). To achieve the change in flow parameter one solution is to change a turbine flow area. As the main turbine flow area meter, varying the first stage turbine vane area in any given turbine provides a prime means for varying turbine flow parameter. Varying turbine vane area may be achieved in various ways including rotating a plurality of the individual vane airfoils in the first stage in any given turbine.
Utilizing rotating turbine vanes to adjust engine by-pass ratio may affect a flow swirl angle to downstream components. The actuation of the rotating vanes alters the inlet angle to the downstream rotor row altering the stagnation location from positive incidence (pressure side stagnation location), neutral incidence (leading edge stagnation location), to negative incidence (suction side stagnation location). This also affects the RPM of first and second blades within the gas turbine engine. In current configurations, the blades may be cooled by cooling air and that cooling air is delivered by a tangential on-board injector (TOBI) that turns the air so that the loss coming on board is minimal. Normally the air is turned in such a way that the incoming velocity is close to that of the blade itself.